CN115151520A

CN115151520A - Side chamber process monitor for adsorptive separation processes

Info

Publication number: CN115151520A
Application number: CN202180015466.7A
Authority: CN
Inventors: J·W·哈里斯; H·A·弗莱茨; 格雷戈里·A·恩斯特; C·A·威廉姆斯
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 2020-02-18
Filing date: 2021-02-11
Publication date: 2022-10-04
Anticipated expiration: 2041-02-11
Also published as: JP2023514305A; EP4107139A4; US20210255152A1; US11249058B2; EP4107139A1; WO2021167829A1; CN115151520B; KR20220140797A; JP7462058B2

Abstract

The invention describes a method for analyzing a stream methods and apparatus for characterizing a fluid. The method utilizes a simulated moving bed system and a rotary valve. The method involves sending a portion of the pump around stream to a side chamber, where the water content of the adsorbent in the side chamber or one or more fluid properties of the stream or both are measured using an analyzer specific to each fluid property.

Description

Side chamber process monitor for adsorptive separation processes

Priority declaration

This application claims priority from U.S. application 16/793,522, filed on month 2 and 18 of 2020, which is incorporated herein in its entirety.

Background

Continuous separation processes are commonly used to separate C from C ₈ The mixture of aromatic hydrocarbons selectively adsorbs para-xylene. Generally, the solid adsorbent used in these processes preferably retains para-xylene in order to separate it from the rest of the mixture. Typically, the solid adsorbent is in the form of a simulated moving bed, wherein the bed of solid adsorbent is kept stationary while the location of the various streams entering and leaving the bed is periodically moved. The adsorbent bed itself is typically a series of fixed sub-beds or modules. The movement of the liquid input and output in position in the direction of fluid flow through the bed simulates movement of the solid adsorbent in opposite directions. The movement of the liquid input and output positions is achieved by a fluid tracking device, commonly referred to as a rotary valve, which cooperates with distributors positioned between the adsorbent sub-beds. The rotary valve achieves the shift input and output locations by first directing the liquid introduction or withdrawal line to a particular distributor positioned between the adsorbent sub-beds. After a specified period of time, referred to as a step time or hold period, the rotary valve advances one index to the next valve position and redirects the liquid inputs and outputs to the dispensers immediately adjacent and downstream of the previously used dispenser. Each advancement of the rotary valve to the next valve position is generally referred to as a valve step, and the completion of all valve steps is referred to as a valve cycle. In one commercial process, the step time is uniform, typically around 60 seconds, for each of the valve steps in a valve cycle. A typical process includes 24 sub-beds of adsorbent, 24 distributors positioned between the 24 sub-beds of adsorbent, two liquid input lines, two liquid output lines and associated purge lines.

Adsorbent systemConsists of four streams, feed, extract, raffinate and desorbent. Each stream flows into or out of the adsorbent system at a particular flow rate, and each rate is independently controlled. The feed introduced to the adsorbent system contains para-xylene, which will be separated from other components in the feed stream. The desorbent introduced into the adsorbent system contains a liquid capable of transferring the feed component from the adsorbent. The extract withdrawn from the adsorbent system contains the desorbent liquid and the separated para-xylene selectively adsorbed by the adsorbent. The raffinate withdrawn from the adsorbent system contains the desorbent liquid and other C in the feed that are less selectively adsorbed by the adsorbent ₈ An aromatic hydrocarbon component. There may also be an associated purge stream introduced into and withdrawn from the adsorbent system. The four main streams are strategically spaced throughout the adsorbent system and divide the sub-bed into four zones, each zone performing a different function.

Zone I contains a sub-bed of adsorbent positioned between the feed input and the raffinate output, and selective adsorption of para-xylene occurs in this zone. Zone II contains a sub-bed of adsorbent positioned between the extract output and the feed input, and desorption of components other than para-xylene occurs in this zone. Zone III contains a sub-bed of adsorbent positioned between the desorbent input and the extract output, and para-xylene is desorbed in this zone. Finally, zone IV contains a sub-bed of adsorbent positioned between the raffinate output and desorbent input. The purpose of zone IV is to prevent contamination of the para-xylene by other components.

A common method for monitoring the water content of the adsorbent chamber is to monitor the feed, desorbent, extract, and raffinate stream water content as bulk fluids. A certain amount of water is injected into the desorbent to maintain the moisture content because a portion of the water is not returned when the extract and raffinate are purified and the desorbent in these streams is recycled back to the adsorbent chamber. However, using a bulk liquid moisture analyzer on only a particular operating area may only give general guidance regarding the moisture in the bulk liquid. This does not allow bulk liquid water content to be measured in all operating regions. More importantly, this does not allow for the measurement of the water content on the adsorbent in the adsorbent chamber.

Another common practice in the industry is to determine the composition distribution of a simulated moving bed separation process of paraxylene by either on-line gas chromatographic analysis or by off-line laboratory analysis. On-line gas chromatography typically requires 10 minutes per analysis, which is significantly longer than the conventional step time of a rotary valve. Thus, only selected valve positions may be sampled and analyzed. Generally, samples are taken and analyzed only in zone II near the extract output and zone IV near the desorbent input. The data provided by such an on-line gas chromatography routine can be used to detect some process anomalies, but unfortunately, analyzing the composition of only two valve positions provides limited information about the performance of the separation process and is only minimally useful for accurate separation process control.

A more in-depth determination of the composition distribution of a simulated moving bed separation process of paraxylene is accomplished using off-line laboratory gas chromatography analysis to determine a value for the concentration of a component in a sample for each valve position in a valve cycle. The measured concentrations are then plotted against their relative valve positions to form a graph generally referred to as a pump cycle curve. Using the pump-around profile, the recovered purity of para-xylene can be calculated and the degree of optimization of the separation can be evaluated. Thus, for example, a desired change in step time and/or liquid stream flow rate can be determined and implemented. A disadvantage of evaluating the separation process in this way is the time delay between sampling and delivery of the analysis results for determining whether or which process changes should be made; manual work involving manually collecting a sample of the material flow; and human exposure where an operator manually collects a sample of the stream from the process. Since the analysis is performed off-line, the time delay can be as long as one day to several days, and can lead to device outages. Because of these disadvantages, refiners typically perform this procedure only once every six months, or if there is a problem with the separation process.

Accordingly, it is desirable to provide methods for determining the water content and pump cycle profile of the sorbent of these systems to provide rapid and frequent analysis of fluid properties with low system maintenance, minimal operator time and labor requirements, and without equipment interruption.

Drawings

FIG. 1 is a schematic representation of one embodiment of the process of the present invention.

Fig. 2 is a more detailed illustration of the side chamber and analyzer of the present invention.

Detailed Description

Adsorptive separations are used to recover a variety of hydrocarbons and other chemical products. The disclosed chemical separation using this method includes: the separation of aromatic hydrocarbon mixtures into specific aromatic hydrocarbon isomers, the separation of linear and nonlinear aliphatic hydrocarbons and olefins, the separation of paraffins or aromatic hydrocarbons from feed mixtures containing both aromatic and paraffinic hydrocarbons, the separation of chiral compounds for pharmaceuticals and fine chemicals, the separation of oxygenates such as alcohols and ethers, and the separation of carbohydrates such as sugars. Aromatic separation comprises a mixture of dialkyl substituted monocyclic aromatics and dimethylnaphthalenes. The main commercial application forming the focus of the previous reference and the following description of the invention without limiting it is from C ₈ The mixture of aromatic hydrocarbons recovers para-xylene and/or meta-xylene.

The present invention is generally used in an adsorptive separation process that simulates countercurrent movement of the adsorbent and surrounding liquid as described above, but the invention can also be practiced in a co-current continuous process as disclosed in U.S. Pat. Nos. 4,402,832 and 4,478,721. Processes for separating the components of a feed stream are discussed in the Handbook of Petroleum Refining Processes,3 rd Edition, chapter 10.3, pages 10.29-10.35 (Chapter 10.3 of the Handbook of Petroleum Refining processes,3d Edition at pages 10.29-10.35), which is incorporated herein by reference.

Optimization of the process in the adsorbent zone requires strict process control of many variables. Of particular interest are methods for optimizing and controlling sorbent chamber moisture (hydration) and stream composition, among others. The method of the invention provides a better understanding of the hydration level at the surface of the adsorbent, which will allow for more precise control of the hydration level of the process. With tighter control, it is possible to improve the production results and extend the life of the adsorbent.

In addition, GC is currently used only during zones II and IV to monitor the composition of the pump around stream. The increase in information regarding the composition of the pump around stream allows for optimization of the zone flow set point in order to operate the process more efficiently.

Additional characteristics may also be measured in the side chamber including, but not limited to, analytical testing of the side chamber adsorbent or adsorbent fines feedback (Δ Ρ information).

The addition of the side chamber system to the pump around stream allows for the installation of small volumes of adsorbent that can be monitored under ideal conditions for analysis. This may include IR or capacitance measurements at the surface of the adsorbent. As the side chamber conditions are further improved and the composition sensors are improved (e.g., micro GC, GC x GC or spectroscopic techniques), the direct optimization of the composition analysis of each region can be enhanced, thereby further improving the overall operation of the process.

The side chamber system may be positioned with the high pressure source at the circulation pump discharge. The outlet from the side chamber system may be returned to the process at the pump tip or downstream of the outlet of the control valve.

One aspect of the invention is a method for analyzing a fluid characteristic of a stream. In one embodiment, the method comprises: providing a simulated moving bed system comprising a plurality of sub-beds of adsorbent in fluid communication with each other and with a rotary valve for separating one or more selectively adsorbed components from a feed stream comprising the one or more selectively adsorbed components and one or more non-selectively adsorbed components; rotating the rotary valve to a first valve position to direct the feed stream to a first sub-bed of the plurality of sub-beds; introducing a portion of the pump around stream between two of the sorbent sub-beds into a side chamber containing sorbent; and measuring, using an analyzer, a water content of the adsorbent in the side chamber or at least one fluid characteristic of the portion of the pump around stream in the side chamber, or both.

In some embodiments, the at least one fluid characteristic comprises at least one of: the water content of the pump around stream, the composition of the pump around stream, or the concentration of the hydrocarbon material of the pump around stream.

In some embodiments, the at least one fluid characteristic is a composition of the portion of the pump around stream, and wherein the analyzer is a gas chromatograph.

In some embodiments, the at least one fluid characteristic is a concentration of hydrocarbon species in the portion of the pump around stream, and wherein the analyzer comprises a spectrometer.

In some embodiments, the at least one fluid characteristic is a water content of the pump around stream, and wherein the analyzer comprises a moisture analyzer.

In some embodiments, the water content of the adsorbent is measured, and wherein the portion of the pump around stream is in direct contact with the adsorbent. In some embodiments, the analyzer is a moisture analyzer.

In some embodiments, the method further comprises: after measuring the at least one fluid characteristic, returning the portion of the pump around stream from the side chamber to the remaining portion of the pump around stream.

In some embodiments, the feed stream comprises C ₈ Aromatic hydrocarbons and the selectively adsorbed component comprises para-xylene.

In some embodiments, rotating the rotary valve comprises rotating the rotary valve to a plurality of valve positions, each valve position directing the feed stream to a different one of the sub-beds, and repeating measuring the at least one fluid characteristic for each valve position of the plurality of valve positions to evaluate the at least one fluid characteristic at each valve position.

In some embodiments, the number of the plurality of valve positions corresponds to the number of the plurality of sub-beds, wherein the number of the plurality of valve positions is 24 defining a full valve cycle, and wherein rotating the rotary valve comprises rotating the rotary valve through the full valve cycle and repeating the measuring of the at least one fluid property until the full valve cycle is completed.

Another aspect of the invention is a method for analyzing a fluid characteristic of a stream. In one embodiment, the method comprises: providing a simulated moving bed system comprising a plurality of sub-beds of adsorbent in fluid communication with each other and with a rotary valve for separating one or more selectively adsorbed components from a feed stream comprising the one or more selectively adsorbed components and one or more non-adsorbed components; rotating the rotary valve to a first valve position to direct the feed stream to a first sub-bed of the plurality of sub-beds; introducing a portion of the pump cycle stream between two of the sorbent sub-beds into a side chamber containing the sorbent, and wherein the portion of the pump cycle stream is in direct contact with the sorbent; the water content of the adsorbent was measured using a moisture analyzer.

In some embodiments, the method further comprises: measuring at least one additional fluid characteristic of the portion of the pump around stream.

In some embodiments, the at least one additional fluid characteristic comprises at least one of: the water content of the pump around stream, the composition of the pump around stream, or the concentration of the hydrocarbon material of the pump around stream.

In some embodiments, the method further comprises: after measuring the characteristic, returning the portion of the pump around stream from the side chamber to the remaining portion of the pump around stream.

Another aspect of the invention is a simulated moving bed system for separating a selectively adsorbed component or components from a feed stream comprising the selectively adsorbed component and a non-selectively adsorbed component or components. In one embodiment, the system comprises: a plurality of sub-beds of adsorbent in fluid communication with each other and comprising two sub-beds in direct fluid communication with each other via a pump-around stream; a rotary valve in fluid communication with each sub-bed of the plurality of sub-beds and configured to rotate to a plurality of valve positions, each valve position directing a feed stream to a different sub-bed of the plurality of sub-beds; a side chamber in fluid communication with the pump around stream; and an analyzer for the characteristic, the analyzer in communication with the side chamber.

In some embodiments, the analyzer is selected from a moisture analyzer, a gas chromatograph, or a spectrometer.

In some embodiments, there are at least two analyzers in the side chamber.

Figure 1 is a schematic diagram of a simulated moving bed adsorption process incorporating the present invention. The process sequentially contacts the feed inlet stream 11 with an adsorbent and desorbent inlet stream 12 contained in a vessel to separate an extract outlet stream 14 from a raffinate outlet stream 13. In a simulated moving bed counter-current system, the progressive downward movement of the various liquid feed and product access points through the adsorbent chamber simulates the upward movement of the adsorbent contained in the chamber. The adsorbent in the simulated moving bed adsorption process is contained in a plurality of beds in one or more vessels; two

containers

100 and 200 are shown in fig. 1 in sequential order. Each vessel containing a plurality of adsorbent beds contacted by a plurality of access points 10 related to the number of beds of adsorbent; the positions of the feed inlet stream 11, the desorbent inlet stream 12, the extract outlet stream 14, and the raffinate outlet stream 13 are moved along the access points to simulate a moving adsorbent bed.

One method of the input and output streams traveling in a loop through a fixed bed of adsorbent is a manifold system, in which valves in the manifold are operated in sequence to effect movement of the input and output streams, allowing the fluid to flow in a countercurrent manner relative to the solid adsorbent. A preferred mode of achieving countercurrent flow of the solid adsorbent relative to the fluid involves the use of a rotary disk valve, wherein the input and output streams are connected to the valve and lines through which the feed input, extract output, desorbent input and raffinate output streams travel in the same direction through the adsorbent bed. Both manifold arrangements and disc valves are known in the art. In the inventive version shown in fig. 1, a disk-type rotary valve 300 as characterized in U.S. Pat. nos. 3,040,777 and 3,422,848, both incorporated herein by reference, effects movement of the stream along the adsorbent chamber to simulate counter-current flow.

Coincident with the simulated upward movement of the solid adsorbent is the movement of liquid occupying the void volume of the packed bed of molecular sieve. To maintain counter-current contact, liquid flowing down the adsorbent chamber may be provided by a pump. Circulating liquid comprising desorbent, extract and raffinate is circulated through the vessel by

pumps

110 and 210 back to the adsorbent chamber via

conduits

111 and 211, respectively. As the active liquid access point moves through the circulation, i.e. from the top to the bottom of the chamber, the chamber circulation pump moves through different zones requiring different flow rates. Programmed flow rate controllers may be provided to set and adjust these flow rates. A system for controlling the flow rate of the circulating liquid is described in U.S. patent 5,595,665, but the details of such a system are not essential to the invention.

The main streams involved in simulated moving bed adsorption as shown in figure 1 can be characterized as follows. A "feed stream" is a mixture containing one or more extract components and one or more raffinate components to be separated by the process. An "extract product" includes the desired components recovered after recovery (typically including fractionation), such as para-xylene or meta-xylene, having a defined purity. The "extract stream" comprises components that are generally the desired product more selectively adsorbed by the adsorbent, along with accompanying desorbent material. The "raffinate product" comprises the less selectively adsorbed components after removal of the extract product. The "raffinate stream" comprises the raffinate product together with the desorbent prior to fractionation. By "desorbent" is meant a material capable of desorbing an extract component, generally inert to the components of the feed stream, and readily separable from both the extract and raffinate.

Purity of the extract productAre often defined with respect to the raffinate component. For example, the para-xylene product impurities can include other C' s ₈ Aromatic hydrocarbons, such as ethylbenzene, meta-xylene and ortho-xylene, optionally together with non-aromatic hydrocarbons and lighter and heavier components. The meta-xylene purity will accordingly relate to the sum of the amounts of ethylbenzene, para-xylene and ortho-xylene. According to this criterion, the product should be at least 99% pure by weight, i.e. at least a ratio of 99 extract to 1 impurity. Preferably, the weight ratio is at least 995 extract to 5 impurities, and typically at least 999. When para-xylene is recovered, the purity can reflect 9999 or higher purity with other C ₈ Weight ratio of aromatic hydrocarbons.

The extract outlet stream 14 and raffinate outlet stream 13 from the illustrated scheme contain desorbent at concentrations between 0% and 100% relative to the corresponding products from the process. The desorbent is typically separated from the raffinate and extract components in raffinate column 400 and extract column 500 as shown in fig. 1 by conventional fractionation and returned to the process in desorbent inlet stream 12. Each of the raffinate column and the extract column includes an appendage as known in the art for condensing and separating the overhead stream and supplying heat to the bottom of the column.

Figure 1 shows that the desorbent is located at the bottom of the respective column, which means that the desorbent is heavier than the extract or raffinate. Recovering an extract product 16 and a raffinate product 15 from the process in respective columns from the extract outlet stream 14 and the raffinate outlet stream 13; from C ₈ The separated extract product of aromatics typically comprises predominantly one or both of para-xylene and meta-xylene, with the raffinate being predominantly non-adsorbed C ₈ Aromatic hydrocarbons and ethylbenzene.

The location of the input and output streams defines the operating zone useful for understanding the present invention. The adsorption zone is defined as the adsorbent positioned between the feed inlet stream 11 and the raffinate outlet stream 13. In this zone, the feedstock contacts the molecular sieve, the extract components are retained, and a raffinate stream is withdrawn. Since the general flow through the zone is from the feed stream entering the zone to the raffinate stream exiting the zone, the flow in the zone is considered to be in the downstream direction when traveling from the feed inlet stream 11 to the raffinate outlet stream 13.

Just upstream with respect to the fluid flow in the adsorption zone I is a purification zone defined as the adsorbent between the extract outlet stream 14 and the feed inlet stream 11. The basic operations that occur in the purification zone are the non-selective void volume shift of the adsorbent from any raffinate material carried into the zone and the shift of any raffinate material retained within the selective pore volume of the molecular sieve. Purification is achieved by passing a portion of the extract stream material exiting the desorption zone into the upstream boundary of the purification zone to effect displacement of the raffinate material. The liquid flow in the purification zone is in the downstream direction from the extract outlet stream 14 to the feed inlet stream 11.

Just upstream of the purification zone with respect to fluid flow is a desorption zone. The desorption zone is defined as the adsorbent between the desorbent inlet stream 12 and the extract outlet stream 14. The function of the desorption zone is to allow the desorbent entering the zone to transfer extract components that remain in the adsorbent during previous contact with the feed in the adsorption zone in a previous cycle of operation. The fluid flow in the desorption zone is in substantially the same direction as the fluid flow in the previous zone.

The buffer zone is defined as the adsorbent between the raffinate outlet stream 13 and the desorbent inlet stream 12 and is positioned directly upstream relative to the fluid flow to the desorption zone. This zone serves to retain the amount of desorbent used in the desorption step, as a portion of the raffinate stream removed from the adsorption zone can be passed to a buffer zone to transfer desorbent present in this zone to the desorption zone. This zone contains sufficient desorbent to prevent transfer of raffinate material present in raffinate outlet stream 13 from the adsorption zone to the buffer zone and further to the desorption zone to contaminate the extract stream removed from the purification zone.

For separating C ₈ Different commercial units of aromatics employ light or heavy adsorbents. If the desorbent is lighter than the extract or raffinate, the desorbent will be recovered from the top of the column and the extract or raffinate will be taken as a bottoms stream, as will be understood by those skilled in the art.

A portion 111A of the circulating liquid (pump around stream) comprising desorbent, extract and raffinate from conduit 111 is sent to the side chamber 600 containing adsorbent. The sample composition varied with the feed to the main chamber and all other ports. The sample to be analyzed is only a very small fraction of that necessary to make the compositional measurements, and will typically be less than 10 gallons per minute (from a flow rate of thousands or tens of thousands of gallons per minute).

Fig. 2 shows an analyzer 610 coupled to the side chamber 600 to measure at least one fluid property of the portion 111A of the circulating liquid. In this manner, one or more fluid properties may be measured. The fluid characteristics may include, but are not limited to, the water content or composition (hydrocarbon concentration) of the portion of the pump around stream. A second moisture sensor 620 may be used to monitor the moisture content of the solid adsorbent 625 inside the side chamber 600. The particular analyzer 610 to be used will depend on the fluid properties being measured and can be determined by one skilled in the art. Suitable analyzers 610 include, but are not limited to, moisture analyzers, gas chromatographs, and spectrometers. When the water content on the adsorbent is to be measured, a portion 111A of the pump around stream is in direct contact with the adsorbent. The performance of the adsorbent is optimal at a specific hydration concentration with water. This hydration is best measured on the adsorbent at the point where the solid material contacts the process fluid. Such measurements will improve the understanding of the sorbent properties compared to measuring only the moisture concentration in the bulk process fluid.

After the portion 111A of the circulating liquid passes through the side chamber 600 and the fluid properties have been measured, the return portion 111B may be returned from the container 200 to the conduit 111 at the suction head of the pump 210. Alternatively, the return portion 111B may be directed at the inlet of the container 100 to the outlet of the chamber circulation control valve 630 on the conduit 111.

A further application of this technique may be used to circulate the bottom material of the container 100 into the parallel system of containers 200 by directing the portion 211A from the conduit 211 to the side chamber 700 at the discharge of the pump 110. The side chamber 700 will be similar in nature to the side chamber 600, but the analyzer used may be different. The return portion 211B will return from the container 100 at the suction head of the pump 110 or to the inlet of the container 200 downstream of the control valve 730.

The rotary valve is rotated to a plurality of valve positions, each valve position directing the feed stream to a different one of the sub-beds. In some embodiments, the at least one fluid property is measured at each valve position. In other embodiments, the at least one fluid characteristic is not measured at each valve position. In some embodiments, one fluid property may be measured at each location, while another property will not be measured at each location. One skilled in the art can determine the appropriate measurement sequence based on the characteristics being measured and the needs of the process.

In some embodiments, the number of the plurality of valve positions corresponds to the number of the plurality of sub-beds, wherein the number of the plurality of valve positions is 24 defining a full valve cycle, and wherein rotating the rotary valve comprises rotating the rotary valve through the full valve cycle, and repeatedly measuring the at least one fluid characteristic until the full valve cycle is completed.

The claimed method can be used to extract a compound from a mixture comprising C ₈ Separation of specific C from a feed stream of a mixture of aromatic hydrocarbons ₈ In a process for the production of aromatic hydrocarbons. For example, in some embodiments, the selectively adsorbing component may comprise para-xylene; in other embodiments, the selective adsorption component may be meta-xylene.

Detailed description of the preferred embodiments

While the following is described in conjunction with specific embodiments, it is to be understood that this description is intended to illustrate and not limit the scope of the foregoing description and the appended claims.

A first embodiment of the invention is a method for analyzing a fluid characteristic of a stream, the method comprising: providing a simulated moving bed system comprising a plurality of sub-beds of adsorbent in fluid communication with each other and with a rotary valve for separating one or more selectively adsorbed components from a feed stream comprising the one or more selectively adsorbed components and one or more non-selectively adsorbed components; rotating the rotary valve to the first valve positionDirecting the feed stream to a first sub-bed of the plurality of sub-beds; introducing a portion of the pump around stream between two of the sorbent sub-beds into a side chamber containing sorbent; measuring a water content of the adsorbent in the side chamber or at least one fluid characteristic of the portion of the pump around stream in the side chamber, or both, using an analyzer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the at least one fluid characteristic comprises at least one of: the water content of the pump around stream, the composition of the pump around stream, or the concentration of the hydrocarbon material of the pump around stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the at least one fluid characteristic is a composition of the portion of the pump around stream and wherein the analyzer is a gas chromatograph. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the at least one fluid characteristic is a concentration of hydrocarbon species of the portion of the pump around stream and wherein the analyzer comprises a spectrometer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the at least one fluid characteristic is a water content of the pump around stream and wherein the analyzer comprises a moisture analyzer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a water content of the adsorbent is measured, and wherein the portion of the pump around stream is in direct contact with the adsorbent. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the analyzer is a moisture analyzer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, the method further comprising, after measuring the at least one fluid characteristic, circulating the pump around the flowFrom the side chamber, the portion is returned to the remainder of the pump around stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the feed stream comprises C ₈ Aromatic hydrocarbons and the selectively adsorbed component comprises para-xylene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein rotating the rotary valve comprises rotating the rotary valve to a plurality of valve positions, each valve position directing the feed stream to a different one of the sub-beds, and repeating measuring the at least one fluid characteristic for each valve position in the plurality of valve positions to evaluate the at least one fluid characteristic at each valve position. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein a number of the plurality of valve positions corresponds to a number of the plurality of sub-beds, wherein a number of the plurality of valve positions of 24 defines a full valve cycle, and wherein rotating the rotary valve comprises rotating the rotary valve through the full valve cycle, and repeatedly measuring the at least one fluid property until the full valve cycle is completed.

A second embodiment of the invention is a method for analyzing a fluid characteristic of a stream, the method comprising: providing a simulated moving bed system comprising a plurality of sub-beds of adsorbent in fluid communication with each other and a rotary valve for separating one or more selectively adsorbed components from a feed stream comprising the one or more selectively adsorbed components and one or more non-adsorbed components; rotating the rotary valve to a first valve position to direct the feed stream to a first sub-bed of the plurality of sub-beds; introducing a portion of the pump cycle stream between two of the sorbent sub-beds into a side chamber containing the sorbent, and wherein the portion of the pump cycle stream is in direct contact with the sorbent; the water content of the adsorbent was measured using a moisture analyzer. An embodiment of the invention is as in the previous embodiment of this paragraph up through the second embodiment of this paragraphIn one, any or all embodiments, the method further comprises: measuring at least one additional fluid characteristic of the portion of the pump around stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the at least one additional fluid characteristic comprises at least one of: the water content of the pump around stream, the composition of the pump around stream, or the concentration of the hydrocarbon material of the pump around stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, the method further comprising returning the portion of the pump around stream from the side chamber to the remaining portion of the pump around stream after measuring the characteristic. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the feed stream comprises C ₈ Aromatic hydrocarbons and the selectively adsorbed component comprises para-xylene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein rotating the rotary valve comprises rotating the rotary valve to a plurality of valve positions, each valve position directing the feed stream to a different one of the sub-beds, and repeating measuring the at least one fluid characteristic for each valve position in the plurality of valve positions to evaluate the at least one fluid characteristic at each valve position.

A third embodiment of the present invention is an apparatus for separating a selectively adsorbed component from a feed stream comprising one or more selectively adsorbed components and one or more non-selectively adsorbed components, the system comprising: a plurality of sub-beds of adsorbent in fluid communication with each other and comprising two sub-beds in direct fluid communication with each other via a pump-around stream; a rotary valve in fluid communication with each sub-bed of the plurality of sub-beds and configured to rotate to a plurality of valve positions, each valve position directing a feed stream to a different sub-bed of the plurality of sub-beds; a side chamber in fluid communication with the pump around stream; and an analyzer for the characteristic, the analyzer in communication with the side chamber. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the analyzer is selected from a moisture analyzer, a gas chromatograph, or a spectrometer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein at least two analyzers are present in the side chambers.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent and can readily ascertain the essential characteristics of the present invention without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. Accordingly, the foregoing preferred specific embodiments are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever, and is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

In the foregoing, all temperatures are shown in degrees celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A method for analyzing a fluid characteristic of a stream, the method comprising:

providing a simulated moving bed system comprising a plurality of sub-beds of adsorbent in fluid communication with each other and with a rotary valve (300) for separating one or more selectively adsorbed components from a feed stream (11) comprising the one or more selectively adsorbed components and one or more non-selectively adsorbed components;

rotating the rotary valve (300) to a first valve position to direct the feed stream (11) to a first sub-bed of the plurality of sub-beds;

introducing a portion (111A) of the pump cycle stream (111) between two of the adsorbent sub-beds into a side chamber (600) containing adsorbent (625);

measuring, using an analyzer (610, 620), a water content of the adsorbent in the side chamber (600) or at least one fluid characteristic of the portion (111A) of the pump around stream (111) in the side chamber (600), or both.

2. The method of claim 1, wherein the at least one fluid characteristic comprises at least one of: a water content of the pump around stream (111), a composition of the pump around stream (111), or a concentration of hydrocarbon species of the pump around stream (111).

3. The method of claim 2, wherein the at least one fluid characteristic is the composition of the portion of the pump around stream (111), and wherein the analyzer (610) is a gas chromatograph.

4. The method of claim 2, wherein the at least one fluid characteristic is the concentration of hydrocarbon species in the portion of the pump around stream (111), and wherein the analyzer (610) comprises a spectrometer.

5. The method of claim 2, wherein the at least one fluid characteristic is the moisture content of the pump around stream (111), and wherein the analyzer (610) comprises a moisture analyzer.

6. The method of any of claims 1 to 5, wherein the water content of the adsorbent (625) is measured, and wherein the portion of the pump around stream (111) is in direct contact with the adsorbent (625), and wherein the analyzer (620) is a moisture analyzer.

7. The method of any of claims 1-5, further comprising:

after measuring the at least one fluid property, returning a portion (111B) of the pump around stream (111) from the side chamber (600) to the rest of the pump around stream (111).

8. The method of any of claims 1 to 5, wherein rotating the rotary valve (300) comprises rotating the rotary valve (300) to a plurality of valve positions, each valve position directing the feed stream (11) to a different one of the sub-beds, and repeating measuring the at least one fluid characteristic for each valve position of the plurality of valve positions to evaluate the at least one fluid characteristic at each valve position.

9. The method of claim 8, wherein a number of the plurality of valve positions corresponds to a number of the plurality of sub-beds, wherein the number of the plurality of valve positions is 24 defines a full valve cycle, and wherein rotating the rotary valve (300) comprises rotating the rotary valve (300) for the full valve cycle and repeatedly measuring the at least one fluid characteristic until the full valve cycle is completed.

10. A simulated moving bed system for separating a selectively adsorbed component or components from a feed stream comprising the selectively adsorbed component and the non-selectively adsorbed component or components, the system comprising:

a plurality of sub-beds of adsorbent in fluid communication with each other and comprising two sub-beds in direct fluid communication with each other via a pump-around stream (111);

a rotary valve (300) in fluid communication with each sub-bed of the plurality of sub-beds and configured to rotate to a plurality of valve positions, each valve position directing the feed stream (11) to a different sub-bed of the plurality of sub-beds;

a side chamber (600) in fluid communication with the pump around stream (111); and

an analyzer (610, 620) for the characteristic, the analyzer in communication with the side chamber (600).